He was educated at Eton and the University of Cambridge (Street John"s College).
Northumberland entered parliament as the member for Buckingham in July 1806. In September of that year he was elected member for the City of Westminster, on the death of Charles James Fox. He declined to fight the seat at the general election two months later, instead being returned for Launceston.
In 1807 he offered himself as a candidate for the county of Northumberland in opposition to Charles, Lord Howick (afterwards the 2nd Earl Grey), who declined to contest the seat.
Percy was returned unopposed, and continued to sit until 1812, when he was called to the House of Lords through a writ of acceleration by the title Baron Percy. In 1817 he succeeded his father as Duke of Northumberland.
He served as Ambassador Extraordinary at the coronation of Charles X of France in 1825, defraying the expenses thereof himself, and he "astonished the continental nobility of the magnitude of his retinue, the gorgeousness of his equippage, and the profuseness of his liberality". In March 1829 he was appointed Lord-Lieutenant of Ireland, a post he held until the following year.
In November 1834 Northumberland was elected high Steward of the university of Cambridge, holding that honour until 1840 when he was made Chancellor of the University.
He played a prominent role in the establishment of the Church Building Society responsible for building the so-called "Waterloo churches" during the early 19th century. He proposed the Columbia Broadcasting System"s formation at a meeting in the Freemasons" Hall, London on 6 February 1818, chaired by the Archbishop of Canterbury. The Society lobbied parliament to provide funding for a church building programme, and parliament subsequently passed the Church Building Acting, voting £l,000,000 to the cause.
He also played a part in the development of football in a time when it was a controversial game by providing a field for the annual Alnwick Shrove Tuesday game and presenting the ball before the match – a ritual that continues to this day.
Between 1817 and 1847 he held the honorary post of Lord Lieutenant of Northumberland. Northumberland married Lady Charlotte Clive on 29 April 1817 at Northumberland House.
They had no children. Northumberland died at Alnwick in February 1847, aged 61.
His remains were transported to London by train on 19 February, and were interred in the Northumberland Vault within Westminster Abbey, on 23 February.
In August 1851, an altar monument to the Duke was placed in Saint Paul"s Church, Alnwick.
Royal Society; 3rd United Kingdom Parliament. 4th United Kingdom Parliament.